Bug 1588192 - Fix the TypeScript require function in the initializers; r=julienw

Differential Revision: https://phabricator.services.mozilla.com/D49012

--HG--
extra : moz-landing-system : lando

devtools/client/performance-new/initializer.js

@@ -3,21 +3,36 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 // @ts-check
 /* exported gInit, gDestroy, loader */
-"use strict";
 
 /**
  * @typedef {import("./@types/perf").PerfFront} PerfFront
  * @typedef {import("./@types/perf").PreferenceFront} PreferenceFront
  * @typedef {import("./@types/perf").RecordingStateFromPreferences} RecordingStateFromPreferences
  */
+"use strict";
+
+{
+  // Create the browser loader, but take care not to conflict with
+  // TypeScript. See devtools/client/performance-new/typescript.md and
+  // the section on "Do not overload require" for more information.
 
   const { BrowserLoader } = ChromeUtils.import(
     "resource://devtools/client/shared/browser-loader.js"
   );
-const { require, loader } = BrowserLoader({
+  const browserLoader = BrowserLoader({
     baseURI: "resource://devtools/client/performance-new/",
     window,
   });
+
+  /**
+   * @type {any} - Coerce the current scope into an `any`, and assign the
+   *     loaders to the scope. They can then be used freely below.
+   */
+  const scope = this;
+  scope.require = browserLoader.require;
+  scope.loader = browserLoader.loader;
+}
+
 const Perf = require("devtools/client/performance-new/components/Perf");
 const ReactDOM = require("devtools/client/shared/vendor/react-dom");
 const React = require("devtools/client/shared/vendor/react");

devtools/client/performance-new/popup/background.jsm.js

@@ -98,6 +98,11 @@ const lazyPreferenceManagement = requireLazy(() => {
  * @type {Map<string, { path: string, debugPath: string }>}
  */
 const symbolCache = new Map();
+
+/**
+ * @param {string} debugName
+ * @param {string} breakpadId
+ */
 async function getSymbolsFromThisBrowser(debugName, breakpadId) {
   if (symbolCache.size === 0) {
     // Prime the symbols cache.

devtools/client/performance-new/popup/initializer.js

@@ -17,18 +17,28 @@
  * Tools -> Web Developer -> Enable Profiler Toolbar Icon
  */
 
-/**
- * Initialize the require function through a BrowserLoader. This loader ensures
- * that the popup can use require and has access to the window object.
- */
+{
+  // Create the browser loader, but take care not to conflict with
+  // TypeScript. See devtools/client/performance-new/typescript.md and
+  // the section on "Do not overload require" for more information.
+
   const { BrowserLoader } = ChromeUtils.import(
     "resource://devtools/client/shared/browser-loader.js"
   );
-const { require } = BrowserLoader({
-  baseURI: "resource://devtools/client/performance-new/popup/",
+  const browserLoader = BrowserLoader({
+    baseURI: "resource://devtools/client/performance-new/popup",
     window,
   });
 
+  /**
+   * @type {any} - Coerce the current scope into an `any`, and assign the
+   *     loaders to the scope. They can then be used freely below.
+   */
+  const scope = this;
+  scope.require = browserLoader.require;
+  scope.loader = browserLoader.loader;
+}
+
 /**
  * The background.jsm.js manages the profiler state, and can be loaded multiple time
  * for various components. This pop-up needs a copy, and it is also used by the

devtools/client/performance-new/typescript.md

@@ -0,0 +1,29 @@
+# TypeScript Experiment
+
+This folder contains an experiment to add TypeScript to Gecko. The type checking is not integrated into continuous integration as of yet, and can be run manually via:
+
+```
+cd devtools/client/performance-new
+yarn install
+yarn test
+```
+
+Also, the types should work with editor integration. VS Code works with TypeScript by default, and should pick up the types here.
+
+## Do not overload require
+
+Anytime that our code creates the `require` function through a BrowserLoader, it can conflict with the TypeScript type system. For example:
+
+```
+const { require } = BrowserLoader(...);
+```
+
+TypeScript treats `require` as a special keyword. If the variable is defined on the page, then it shadow's TypeScript's keyword, and the require machinery will be improperly typed as an `any`. Care needs to be taken to get around this. Here is a solution of hiding the `require` function from TypeScript:
+
+```
+const browserLoader = BrowserLoader(...);
+
+/** @type {any} - */
+const scope = this;
+scope.require = browserLoader.require;
+```